When M/K got the cars to be GOH'ed, some cars needed more work than others. So, if one car of a set was finished and the other wasn't, rather than hold the completed car, they mated it with another car whose natural mate was not finished also. So, we wound up mis-mates. Additional mis-mates off the top of my head are 3444/3777, 3445/3468. There are many, many more. The complete list of mis-mates are in the Retired/R32 section in the following website: "nycsubway.org."